Rotor and method for making same

Abstract

A rotor adapted for use in a motor and a fan. The rotor has a cup-shaped rotor body made of synthetic resin materials. A shaft is coaxially coupled with a bottom of the rotor body so as to expose a part of one end of the shaft to outside of the rotor body. And the bottom of the rotor body includes an annular recess coaxially formed with the shaft on an outer surface of the rotor body, an annular projection is coaxially formed with the shaft so as to surround the exposed portion of the shaft on the outer surface of the bottom of the rotor body. The exposed portion of the shaft and the annular projection are accommodated in the annular recess.

What is claimed is: 
     
       1. A method for making a rotor having a cup-shaped rotor body and coaxially coupled with a shaft so as to expose a part of one end of the shaft to outside of the rotor body comprising: positioning the shaft at a predetermined portion within a cavity of a mold having a corresponding configuration with the rotor;   fixing the shaft to a center pin having an fixing hole for fixing an end of the shaft;   injecting a melting synthetic resin into the cavity through a gate coaxially surrounding the shaft fixing portion of the center pin and opening toward the cavity;   taking out the rotor from the cavity and cutting off an extra synthetic resin which is hardened in the vicinity of the opening of the gate.   
     
     
       2. A method of claim 1, wherein the marks of the cutting off the extra synthetic resin forms an annular projection coaxially formed with a shaft so as to surround the exposed portion of the shaft on an outer surface of a bottom portion of the rotor body. 
     
     
       3. A method of claim 2, wherein a part of the gate projects into the cavity and forms an annular recess on the outer surface of the bottom of the rotor body, the exposed portion of the shaft and the annular projection are accommodated in the annular recess.